Often the problem is that the guy who has made something his career posts incorrect things more often than the guy who hasn't. Some of the reasons for these are:

- self-interest

  - intentionally since it protects their interests

  - accidental since they've spent so much time they need it to be meaningful

  - accidental since they want to please their fellow experts

  - intentionally since they want to go with the herd

- selection bias towards being someone who cares about this very much goes with lack of aptitude

- historical bias

  - most people are better equipped than experts to spot paradigm shifts because experts are over-indexed on the status quo

- no field expertise

Ultimately, it's up to you how you weight people's opinion, and may each person's epistemology serve them appropriately.

It's not the more they know, it's the more credentials they have. Which is not the same, often wildly so.

Oh so you mean "expert" as in "labelled expert by someone" not actually "someone who is an expert"?

What do we call the actual experts then so that we don't confuse them with nonexperts with credentials?

Unfortunately, the uneducated and uninformed tend to hold the strongest opinions.